Method of machining out-of-round piston-ring castings



C. E. JOHNSON. METHOD OF MACHINING OUT-OF-ROUND PISTON RING CASTINGS.

APPLICATION FILED SEPT-7,1920.

1 ,4O5 5 17, Patented Feb. 7, 1922.

FFHE.:

CHARLES E. JOHNSON, 0F MUSKEGON, MICHIGAN.

METHOD OF MACHINING OUT-OF-ROUND PISTON-RING- CASTING-S.

Specification of Letters Patent.

Patented Feb.

Application filed September 7, 1920. Serial No. 408,506.

To all whom it may concern:

Be it known that 1, CHARLES E. JOHNSON, a citizen of the United States of America, residing at Muskegon, in the county of lVIuskegon and State of Michigan, have invented certain new and useful Improvements in Methods of Machining Out-of- Round Piston-Ring Castings; and I do hereby declare the following to be a full,

circular but is what is known as out-of round. Ring castings of this type may be made according to the method shown and described in the patent to Campbell, issued January 14, 1913, No. 1,050,102, in which the pattern includes an additional piece or segment disposed in the length of a ring casting and which when removed and the ends brought together makes a truly circular ring. Accordingly, the casting with this additional length included therein is of a slightly oval type and is not truly circular My method of machining castings made in this or an equivalent manner is directed to forcing the ring casting of out-of-round formation to a circular form and machining it while in such circular form.

For an understanding of the invention and the manner in which it is practiced, reference may be had to the following description taken in connection with the accompanying drawing, in which:

Fig. 1 is an elevation showing an out-ofround ring casting in full lines, substantially the circular form which it will take when parted and a piece removed therefrom being shown indotted lines.

Fig. 2 is a fragmentary elevation of the immediate operating parts used in one type of machine for practicing my method, the ring between said parts being shown in section.

Fig. 3 is a front elevation of a lathe which may be used in carrying out the method, and

Fig. 4 is an end elevation of one of the members usedto act upon a ring casting in the out-of-round form and distort it into perfectly circular form for machining,'the

two forms of the ring casting being shown in full and dotted lines against the end of said member.

Like reference characters refer to like parts in the different views of the drawing.

The ring casting 1 is aclosed ring of a length equal to the length of the finished piston ring plus shrinkage and allowance for finishing with an additional amount equal to the gap between the ends of a finished piston ring in its normal uncompressed shape. This additional amount is indicated between dotted lines of the ring casting l at 2 in Fig. 1, and when said amount is cut from the ring casting and the ends brought together a perfectly circular ring is made which will bear with even pressure against all sides of the cylinder in which it is placed.

It is evident that the ring casting made by pouring molten iron into a mould has to be finished in order to make a finished piston ring. Heretofore it has been the practice to rough grind the outer curvedsurface of the rough ring castings and then pass the same between suitable testing gauges for thickness tests. Certain castings which would not pass at some points in their length between said gauges were marked and returned forfurther rough grinding until the requisite approximate uniformity of thickness of the casting was attained. The ends of the casting were finished in any suitable manner, the same not being of importance in connection with the present invention as the same methods are still used for this. The gap piece was then cut from the ring, the ring compressed and the ends brought together and clamped so as to hold the ring casting into circular form, a roughing cut taken on the outer surface of the ring and finally the finishing cut was taken with the ring casting still in the compressed form. 1

My method is to take the ring castings as they come from the mould and, after finishing the same on the ends in any desired manner, distort said ring castings from their out-of-round condition to a. form which is circular and then take the first or roughinv cut from the outer surface while it is held to said circular form. This dispenses entirely with three operations in the finishing of piston rings from the ring casting, namely, the test-ing of the rough ground rings for thickness, also the rough grinding heretofore used and the rough milling operation necessarily used heretofore in cutting the gap piece out of the ring casting, and with quantity production methods of modern manufacture and the handling of many thousand rough ring castings such operations are a matter ofconsiderable expense in piston ring manufacture, particularly as many of the rings must be returned. for further grinding to remove extra thickness of metal at various points l Vith my method any excess of metal is removed with the roughing cut made while the ring casting is held to circular form. v

Gne mechanism for ei'fectively practicing the method is shown in Figs. 2, 3 and 4C. A lathe is used and on the head and tail stock spindles thereof ring holding members are mounted. The member mounted on the head stock spindle is a head 3 which at its free end is formed with a conical annular face 4:, the same being hardened and against which the ring is forced. The opposite member is a cylindrical head 5 having a fiat face 6 which comes against the opposite end of the ring and forces .it firmly against the conical end 4 of the cylinder 3.

The member '3 is fixed in any suitable manner on the head stock spindle. The head '5 is attached to the tail stock spindle 8 which is of any suitable quick action type being moved back and forth through the tail stock through a link 9 operated by a handle 10. The head 5 when moved toward the member 3 engages so as-to turn therewith, a series of openings 11 in the end of the member 3 being located so that any one of them may receive the pin 12 projecting to cause said distortion.

from the head 5.

When a ring casting, such as 1, is placed against the conical surface 4 and the head 5 with its vertical flat surface 6 brought against the opposite side of the ring casting, said casting is distorted out of its normal shape into true circular form. The pressure of the head 5 against the ring is sufiicient The ring casting being held 1 between the "members 3 and 5 turns therewith and any suitable cutting or grinding tool may be brought against the casting and fed along the same from one end to the other thereby removing the outer rough portions of the casting andleaving it in shape such that when the gap piece is cut from the ring casting (and this may be done in one operation, instead of two as heretofore required) it requires only the compression of the ring casting to circular form and a finishing of the same by a sin 1e finishing cut across its outer surface. he distortion of the ring casting from its out-ofinoaair round shape to circular form does not strain the metal and as soon as the ring casting is removed from between the heads 3 and 5 it resumes its normal out-of-round form.

This method of handling ring castings for machining the outer curved surfaces thereof has proven particularly satisfactory in practice and is of value in piston ring manufacturing, due to the elimination of operations which have heretofore been considered necessary. The rough grinding, testing of the rings for thickness and one. milling operation in cutting the slot in the ring are done away with entirely by reason of the distortion of the rough, continuous, out-ofround casting to circular form and its finishing at its curved outer surface prior to the cutting of the slot in the ring. The method which I have-devised may be carried out in various ways and l do not wish to be restricted to any particular specific mechanism in practicing the same. The mechanism which I have devised for effectively practicing the method is the subject matter of a separate application and its, specific construction will be disclosed and claimed therein.

The ring casting when distorted from its I normal out-of-round form to circular form may be machined in different ways. lln practice T have rotated the ring holding heads and the ring casting held between the same at high speed and fed a cutting tool lengtha out-of-round casting to true circular ormv may be used irrespective of the type or kind ofwork which is done at the outer surface thereof whether rough cutting by a suitable tool, running a grinding wheel lengthwise of the casting to grind the same or any other machine process for finishing or helping to finish the outer curved surface of the ring.

The inventionis defined in the appended claims and I consider myself entitled to all modifications of structure which fall within their scope.

ll claim:

1. The herein described method of machining piston ring castings which consists in distorting a continuous out-of-round ring casting to circular form and machining the same at its outer curved surface while it is held to said circular form, substantially as described. 2. The herein described method of machin ing an individual piston ring casting which consists in providing a continuous ring casting normally cast in an out-of-round form,

forcin said continuous ring casting to'circular orm and holding the same to said cir cular form and machining the casting at the outer curved surface thereof while it is held to said circular form, substantially as and for the purposes described.

3. The herein described method of machining piston ring castings which consists in providing a continuous individual ring castin of out-of-roundform, forcing it to circu ar form, holding it to said circular form, rotating the same about its central axis and machinlng the casting at its outer curved l.

surface while it is held to said circular form and rotated, substantially as described.

at. The herein described method of machining piston ring castings which consists in provlding an individual ring casting'of outof-round form, placing one end of the casting against a conical surface, pressing the ring to circular form by pressure applied to the opposite end of the ring sufiicient to force the ring into contact at all points with said conical surface and thereafter machining the ring casting at its outer curved surface while it is held to said circular form, substantially as described.

5. The herein described method of machining piston ring castings which consists in providing an individual ring casting of outof-round form, placing one end thereof against a conical surface, bringing a head to and holding it against the opposite end of the ring and pressing the same against the ring to thereby force the casting to circular formagainst said conical surface and machining said ring casting at its outer curved surface while thus held to circular form, substantially as and for the purposes described.

6. The herein described method of machi'n: ing piston ring castings which consists in distorting an out-of-round ring casting to circular form and machining the same at its outer curved surface While it is held to said circular form, and thereafter cutting 

